In a review article published in September
2000, researchers summarize and critique the findings of controlled
clinical trials on St. John's wort, kava, ginkgo, and valerian
published since 1991. Reviewers found the evidence for St. John's
wort's efficacy the most convincing, with five of nine studies
showing it to be superior to placebo, and the other four finding
the herb to be as effective as prescription antidepressants. They
believe that poorly defined patient populations, small sample
sizes, short treatment duration, and nonstandard measures of symptoms
make the positive results of many of the kava and ginkgo studies
less credible. Thirty-nine of the 40 ginkgo trials reviewed found
that the extract significantly improved memory, concentration,
fatigue, anxiety, and depression in patients with dementia.
Psychiatric Services, September 2000.